The present invention relates to a pressure sensor which detects a fluid pressure. More particularly, it relates a pressure sensor which detects pressure of various types of gas or chemical, such as chemicals used for a semiconductor producing process.
A conventional pressure sensor will be explained in the following.
The conventional pressure sensor has a conduit which constitutes a passage for flowing a fluid, such as chemical, from one end to the other end thereof. Small space (dead space) is formed on the part of the passage, and a thin diaphragm for receiving fluid pressure directly is disposed above the dead space.
A sensor head is disposed on the diaphragm and has a pressure sensitive area responsive to the fluid pressure. The pressure sensitive area contacts the diaphragm. The pressure sensitive area of the sensor head is positioned on the passage via the dead space and the diaphragm. In such a structure, the pressure in the passage is transmitted to the pressure sensitive area of the sensor head via the fluid, which is trapped in the dead space, and then the diaphragm.
When the pressure sensor is used, both ends of the conduit are first connected to a piping for flowing fluid such as chemicals. And then, when the fluid is flowed through the passage, the fluid is trapped in the dead space. The fluid pressure is transmitted to the diaphragm via the trapped fluid and then the pressure acting on the diaphragm is detected by the pressure sensitive area of the sensor head.
In the conventional pressure sensor, since the dead space is formed on the part of the passage and the diaphragm is disposed above such the dead space, air or fluid may be remained in the dead space when the fluid is flowed through the passage. Accordingly, the dead space should be eliminated and a pressure sensor without dead space is required.
In view of the problems, the object of the present invention is to provide a pressure sensor in which dead space is not formed under the diaphragm so that air or fluid is not remained in the sensor.
In order to solve the problems, the present invention provides a pressure sensor, having a passage for flowing fluid from one end to the other end thereof, comprises a sensor head having a pressure sensitive area responsive to the fluid pressure, and a diaphragm having a pressure receiving surface for receiving the fluid pressure directly, wherein said pressure receiving surface is disposed so as to protrude to the inside of the passage, and said pressure sensitive area is disposed on the opposite surface from the pressure receiving surface of the diaphragm.
Here, the fluid means both gas and liquid.
In said pressure sensor, since the pressure receiving surface is disposed so as to protrude into the inside of the passage, dead space will not be formed under the diaphragm. In this structure, air and fluid will not be remained in the sensor.
And, in said pressure sensor according to the present invention, the sensor head may be covered with the diaphragm.
And, in said pressure sensor according to the present invention, it is preferred that an air hole for escaping air near the sensor head to the outside is formed at the diaphragm. In this manner, the fluid pressure will be detected accurately.
And, in said pressure sensor according to the present invention, it is preferred that the fluid pressure in the passage is transmitted to the pressure sensitive area via the pressure receiving surface.
And, said pressure sensor according to the present invention may further comprise a conduit which constructs the passage.
And, said pressure sensor according to the present invention may further comprise a body which is integrally formed with the conduit.
And, in said pressure sensor according to the present invention, it is preferred that the body has a through bore which communicates with the passage, the trough bore being provided with the diaphragm and the sensor head.
And, in said pressure sensor according to the present invention, it is preferred that the conduit is connected to a piping for flowing a fluid at both ends thereof.
And, in said pressure sensor according to the present invention, it is preferred that the diaphragm is made of fluororesin.